A formwork block is classically comprised of two insulating elements spaced apart and connected by a structure, preferably a metal one. For reasons of heat and sound, it is advantageous to use polystyrene foam. This material is used in the rest of the specification, but only for illustrative purposes.
One is familiar from FR-A-2 132 597 with a method of fabrication of a wall by formwork, using a lost casing in the form of hollow assembled building blocks, and in which concrete is poured. Even so, such a formwork still requires an external insulation.
Furthermore, FR-A-2 556 387 specifies a construction element designed to form an insulating formwork to make a wall by pouring concrete into it. This block has a set of regularly spaced apertures to accommodate rods for positioning the blocks relative to each other. Moreover, the vertical edges have a means of assembly with another adjacent block.
Finally, FR-A-2 531 988 discloses an insulating formwork with different component modules, namely, a module of normal size, a half-module to allow for the staggering between two courses, an end module, and a half-end module.
Even so, one of the problems involved in the formwork blocks is that the two elements making up a formwork block need to have a sufficient mechanical strength to resist the load and the pressure created by the poured material. Thus, this is characterized by the use of a particularly costly insulating material. Furthermore, in order to further augment the insulation for a structure in which such a block is used, it is desirable to increase the thickness of the element that is located on the outside. This, then, results in a great increase in the material cost, since the outer element is contiguous, and thus made from one and the same material. Another problem caused by the increase in asymmetric material is the formation of residual thermal deformations. The cooling time is also greatly increased.
In order to obtain a structure resistant to moisture, U.S. Pat. No. 1,441,362 describes a hollow construction block comprised of two pieces, assembled together, of such shape that when assembled they define both a horizontal conduit and a vertical conduit for air passage. This disclosure, however, is not adapted to insulating formworks, which need to guarantee the proper flowing and filling of the concrete, as well as resist the pressure created by the mass of poured material.
DE 200 03 380 discloses a formwork block having two walls, one of them comprising an element applied by a slider. The lack of an end stop for this slider, however, has the consequence that the weight of the outer surfacing may result in a progressive downward movement of said element, since it is not supported by the rest of the block.
FR 2 594 158 discloses a device for fixation of a layer of insulator on cinderblocks. The layer of insulator is placed against the cinderblock thanks to projecting tenons, cooperating with grooves made in the cinderblocks. The vertical support here is provided only by the cross section of the tenons, in the plane of the wall, which can prove to be inadequate. Furthermore, the grooves emerge into the cavity receiving the concrete, which can be a cause of leakage of material.
The purpose of the present invention is to remedy at least some and preferably all of these drawbacks by proposing a formwork block having enhanced insulating capabilities, a low manufacturing cost, and sufficient mechanical strength to support the poured material.